The disclosed technology relates to non-halogen flame retardant compositions comprising phosphorus in complex with nitrogen, and cross-linked by a cross-linking agent, such as resorcinol.
Halogens, i.e., fluorine, chloride, bromine and iodine, can be used in fire retardant compositions. However, organic compounds containing halogens can generate toxic substances, such as dioxin and difuran, upon combustion. Organohalogens may also accumulate in the human body for long periods of time and cause hormone problems. In addition, fluorine, chloride and bromine in particular, have been known to cause severe depletion of ozone. For this reason, the use of halogens, whether as flame retardants or in other applications, is increasingly regulated. Accordingly, there is a need for non-halogenated flame retardants.
One method of obtaining a flame retardant composition is to include phosphorus in the composition. For example, U.S. Pat. No. 5,281,239 to Chatelin et al., issued Jan. 25, 1994, teaches a method of grafting a fibrous material with phosphoric acid ethylenic esters of the general formula:
the graft rate of the ester is taught to be less than or equal to 20%.
Similarly, U.S. Publication No. 2010/0261862 to Sugiyama et al., published Oct. 14, 2010, teaches a method for grafting phosphorus containing compounds along with an amine compound onto a cellulosic fiber. The method relies on irradiating the fiber to create radicals to which the phosphorus containing compound may bind.
JP2007182652A to Toshio, published Jul. 19, 2007, teaches flame retardant additives comprising a mixture of an organic phosphorus-base-flame-retarder and a nitrogen type flame retardant. Similarly, CN 102071032 teaches the use in combination of phosphorus containing and nitrogen containing flame retardants. These publications only teach compounds containing tribasic phosphoric acid and do not teach polymerizing the compounds.
Polymer compositions containing a rubber modified vinyl resin, a polyphenylene ether resin, a cyclic alkyl phosphate compound, and an aromatic phosphate ester are taught in U.S. Pat. No. 7,829,629 to Ahn et al., issued Nov. 9, 2010. Similarly, U.S. Publication No. 2007/0192966 to Cottrell et al., published Aug. 23, 2007, teaches flame retardant phosphorus containing polymers comprised of between 10 and 100 wt. % of phosphorus containing monomer derived units. Neither of the aforementioned references teaches a polymer in which the monomers are in complex with an amine species. These polymers would be highly acidic and damaging to various substrates and thus, a transport concern.
A further problem exists in that some non-halogenated flame retardant polymers do not remain coated on a surface if and when the surface is contacted with water. For example, some surfaces are often contacted, or subject to be contacted with tap water. If the flame retardant coating washes off with the tap water, the surface will lose its flame retardance.
A need exists for new non-halogenated flame retardants, and particularly non-halogenated flame retardant polymers that less readily wash off with water.